Compositions for the washing and cleaning of hard non-textile surfaces occurring in the home and in the institutional sector are generally intended to generate little foam in use, the foam they do generate being expected to collapse significantly in a few minutes. Compositions of this type are well-known and established on the market. They are essentially aqueous surfactant solutions of various kinds with and without added builders, solubilizers (hydrotropes) or solvents. Although the consumer prefers the in-use solution to foam to a certain extent at the beginning of the cleaning task as proof of effectiveness, the foam is expected to collapse rapidly so that cleaned surfaces do not have to be rewiped. To this end, low-foaming nonionic surfactants are normally added to compositions of the type mentioned.
Today, machine-washed tableware has to meet stricter requirements than hand-washed tableware. Thus, even tableware completely free from food residues is regarded as unsatisfactory when, after dishwashing, it still has whitish stains which are attributable to water hardness or other mineral salts and which come from water droplets that have remained on the tableware through lack of wetting agent and dried.
Accordingly, to obtain bright, spotless tableware, rinse agents have to be used. The addition of liquid or solid rinse agent—which may be separately added or which is already present in ready-to-use form together with the detergent and/or regenerating salt (“2-in-1”, “3-in-1”, for example in the form of tablets and powders)—ensures that the water drains completely from the tableware so that the various surfaces are bright and free from residues at the end of the dishwashing program. Commercially available rinse agents are mixtures of, for example, nonionic surfactants, solubilizers, organic acids and solvents, water and optionally preservative and perfumes.
The function of the surfactants in these compositions is to influence the interfacial tension of the water in such a way that it is able to drain from the tableware as a thin, coherent film so that no droplets of water, streaks or films remain behind during the subsequent drying process (so-called wetting effect). Accordingly, another function of surfactants in rinse agents is to suppress the foam generated by food residues in the dishwashing machine. Since the rinse agents generally contain acids to improve the clear drying effect, the surfactants used also have to be relatively hydrolysis-resistant towards acids.
Rinse agents are used both in the home and in the institutional sector. In domestic dishwashers, the rinse agent is added after the prerinse and wash cycle at 40 to 65° C. Institutional dishwashers use only one wash liquor which is merely replenished by addition of the rinse agent solution from the preceding wash cycle. Accordingly, there is no complete replacement of water in the entire dishwashing program. Because of this, the rinse agent is also expected to have a foam-suppressing effect, to be temperature-stable in the event of a marked drop in temperature from 85 to 35° C. and, in addition, to be satisfactorily resistant to alkali and active chlorine.
In addition, it should be possible through the use of rinse agents to finish the surfaces to be cleaned in such a way that soil is easier to remove in the next dishwashing cycle.
DE-A1 19738866 describes surfactant mixtures of hydroxy mixed ethers and nonionic surfactants, such as optionally end-capped fatty alcohol polyethylene glycol/polypropylene glycol ethers, which have favorable foaming behavior and show good clear rinse effects in rinse agents. It is known from German Offenlegungsschrift DE-OS 2432757 that hydroxy mixed ethers can be used as foam suppressors in laundry detergents, dishwashing detergents and cleaning compositions.
The problem addressed by the present invention was to provide surfactant mixtures for the production of dishwashing detergents and cleaners which, at one and the same time, would show good foaming and cleaning behavior, but especially favorable drainage behavior, through improved wetting behavior on various surfaces. The cleaned surfaces would thus create a particularly good visual impression distinguished by greater sparkle. In addition, high material compatibility, particularly with plastics, would be guaranteed and solid cleaning formulations would be easier to produce. Also, the surfaces to be cleaned or rinsed would be left with such a finish that soil would be easier to remove in the next cleaning cycle.
The problem stated above has been solved by the combination according to the invention of hydroxy mixed ethers and polymers in the mixing ratio according to the invention. A spotless shine of the surfaces to be cleaned is obtained through the very favorable wettability. The effect of adding polymers to rinse agents is that otherwise firmly adhering and often critical soils, for example starch-containing soils, can be completely removed in the next cleaning cycle. These soils can be removed without additional manual treatment of the tableware.